Cryptanalysis of block based spatial domain watermarking schemes

In this paper we propose a block based method of image reconstruction which acts as a generic attack against any block based watermarking scheme in spatial domain. Our reconstruction method relies on the geometric features of the image,to discover and modify the inconsistencies in the pixel values introduced due to watermarking. To show its effectiveness we mount the attack on a few existing watermarking schemes. These schemes divide the image into some disjoint sets of pixels. Intensities of constituent pixels of each such set is modified to embed one bit of watermark. And the watermark is a secret binary string which comes from error correcting code..,In the process of cryptanalysis we reconstruct an image from a single watermarked copy. Experimental result shows that from the attacked image, watermark extraction becomes impossible, making cryptanalysis successful.